doesn't send email on zoho

i have smtp plugin, i can send emails though it that is hosted under zoho.
i tried both methods from my server using php or smtp.
the status is sent, but never delivered.
i tried hosted method and copied same zoho settings, also doesnt work.

let me know if there is a debug option that shows what happened when i test send an email please.

https://wordpress.org/plugins/wysija-newsletters/